Bug 680903

Summary: incorrect real time signals
Product: [Fedora] Fedora Reporter: Karel Zak <kzak>
Component: straceAssignee: Roland McGrath <roland>
Status: CLOSED NOTABUG QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 14CC: dvlasenk, ldv, roland, schwab
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Fixed In Version: Doc Type: Bug Fix
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Last Closed: 2011-02-28 13:34:18 UTC Type: ---
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Description Karel Zak 2011-02-28 12:24:10 UTC 
Description of problem:

strace(1) incorrectly translates the second kill(2) argument from signal number to SIGRT_<N> if the argument is real-time signal.

For example the following code uses SIGRTMIN+10, but strace(1) prints SIGRT_12:

---
#include <stdio.h>
#include <sys/types.h>
#include <signal.h>

int main(int argc, char **argv)
{
        return kill(atoi(argv[1]), SIGRTMIN + 10);
}
---

$ sleep 1000 &                                                                               [1] 9192

$ strace -e kill ./a  9192 
kill(9192, SIGRT_12)                    = 0
           ^^^^^^^^

[1]+  Real-time signal 10     sleep 1000
Comment 1 Dmitry V. Levin 2011-02-28 13:34:18 UTC 
$ cat s.c
#include <stdio.h>
#include <unistd.h>
#include <signal.h>

int main(void)
{
	printf("SIGRTMIN=%d, __SIGRTMIN=%d\n", SIGRTMIN, __SIGRTMIN);
        return kill(getpid(), SIGRTMIN + 10);
}

$ strace -ekill ./s
SIGRTMIN=34, __SIGRTMIN=32
kill(13589, SIGRT_12)                   = 0
--- SIGRT_12 (Real-time signal 10) @ 0 (0) ---
+++ killed by SIGRT_12 +++
Real-time signal 10

Note that SIGRTMIN != __SIGRTMIN.
The first is defined by glibc, the latter is defined by kernel headers.
This difference is documented in signal(7).

There should be no surprise that strace prints kernel constants while strsignal(3) prints glibc constants.